There are two main reasons why the underlying structure isn't exposed. I was wondering how long it would take for people to notice...guess most folks don't tweak
First, they use IP that belongs to Gibson and which I acquired while doing sound design for the Firebird X. So the good news is we have access to it because it's Gibson's. The bad news is I would be violating the NDA I signed while working on the Firebird X if I exposed the IP. Violating an NDA is a non-starter for me. However, most of the Anderton Collection effects do use a conventional FX chain and do expose the parameters, because there's nothing proprietary about them.
Second, those amps are like a house of cards. You make one little change, and they turn into "suck" very fast. For example one amp has 24 stages of EQ. If you bypass just one of those stages, it falls apart. They do a lot of things "wrong" and if you try to apply conventional programming tweaks, your head will explode. I spent a year (off and on) working on those amps, and I don't think you can do much more optimizing.
There are two other reasons that are more conceptual. I really wanted these to be plug-and-play where people could just drag them into a project and have them work. Also, removing the strip along the bottom of the traditional FX chain (the amp ones are slightly different) makes it look a lot nicer.